Benzoic acid biosynthesis in cell cultures of Hypericum androsaemum
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Biosynthesis of benzoic acid from cinnamic acid has been studied in cell cultures of Hypericum androsaemum L. The mechanism underlying side-chain shortening is CoA-dependent and non-β-oxidative. The enzymes involved are cinnamate:CoA ligase, cinnamoyl-CoA hydratase/lyase and benzaldehyde dehydrogenase. Cinnamate:CoA ligase was separated from benzoate:CoA ligase and 4-coumarate:CoA ligase, which belong to xanthone biosynthesis and general phenylpropanoid metabolism, respectively. Cinnamoyl-CoA hydratase/lyase catalyzes hydration and cleavage of cinnamoyl-CoA to benzaldehyde and acetyl-CoA. Benzaldehyde dehydrogenase finally supplies benzoic acid. In cell cultures of H. androsaemum, benzoic acid is a precursor of xanthones, which accumulate during cell culture growth and after methyl jasmonate treatment. Both the constitutive and the induced accumulations of xanthones were preceded by increases in the activities of all benzoic acid biosynthetic enzymes. Similar changes in activity were observed for phenylalanine ammonia-lyase and the xanthone biosynthetic enzymes benzoate:CoA ligase and benzophenone synthase.
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